The present invention is related to an apparatus for using a plurality of electron beams to inspect for defects, etc., in patterns formed on the surface of a sample; and in particular, to an apparatus for performing high-throughput wafer defect detection (such as, for example, in a semiconductor device fabrication process) by irradiating the sample with an electron beam; detecting secondary electrons (which vary according to the properties of the surface of the sample); forming image data therefrom; and inspecting and evaluating patterns, etc., formed on the surface of the sample, based on that image data. It is also related to a device fabrication method for high yield production of semiconductor devices, using such an apparatus.
Conventional systems using scanning electron microscopes (SEM) are currently available for performing the above wafer inspection function. These systems form an SEM image by raster-scanning a finely focussed electron beam over an extremely closely spaced raster width, while detecting secondary electrons emitted from the sample using a secondary electron detector. Defects are then found by comparing the SEM image with a reference standard image.
Because of the small beam size, pixel size, and raster width used in SEM systems adapted for defect inspection, however, such inspections required a huge amount of time. Also, when the sample was irradiated with a larger beam to improve throughput, this produced degraded spacial resolution quality of the SEM images.
Multibeam inspection systems, in which the sample is irradiated with a number of beams at the same time, have also been in development over the past few years. Many improvements to such systems are needed, however, for realization of high throughput, while also maintaining good precision.